In selecting plastics for parts it has been the practice to make the selection based on bulk properties or alternatively by testing the performance of a prototype.
Frequently the bulk properties of a plastic do not prove to be the best indicator of how a plastic will perform when used for a part since parts are often made from components which are assembled and held together by various fastening and bonding techniques. In the parts which result the performance is frequently determined by the performance of the fasteners and the bonding between the components.
In other parts a processing step, such as injection molding, can limit the suitability of a plastic for a particular application since the processing steps may introduce distortions in the part.
Still in other situations the part may be successfully molded and assembled, provide adequate strength and dimensional stability, only to deteriorate when exposed to elevated temperatures or to thermal cycling.
Thus there is a need for a test specimen that will provide information of the performance of materials in three dimensional shaped forms and reduce the need to build prototypes for preliminary testing. The test specimen needs to be suitable for testing the performance of plastics as a function of the method of assembly and provide comparative data on the effect of time at temperature and the effect of thermal cycling on the properties of fabricated test specimens.